Abrading device



D -10.1940. E. D. "Lu/ER Em 2.224368 ABRADING DEVICE Filed June 24, 1938m RWL Y 0/. E mum m I A 35 drawing Patented l0, 1940 nnnnnme nuvlcu I mmD. 'rmye r and Harold B- Moulton, South Q bridge, Masa, gnors toAmerican Optical- Compan Sou bridge, Mass-, a voluntary sociation ofMassachusetts Application June 24, 1938, seen No. 215,592

This invention relates to improvements in abrading devices'and hasparticular reference to improved means andmethods of supporting worktobeabraded. 4

5 One of the principal objects or the invention is to provide improvedmeans and methods of blocking articles formed of resinous material;which will avoid injuring a highly polished finished surface on the sideof the article adjacent to the i block.

Another object of the invention is to provide improved means and methodsof blocking lenses having theabove characteristics. whereby the lensesmay be quickly and easily positioned on the 15 holding means and arereadily removable without being injured. A

, Another object of the invention is to provide a method of blockinglenses having the above characteristlcs whereby the surface engaging the20 block or holdingmeans isprotected against injury during the blockingoperation.

Another object is to provide a tight seal between the lens or'articleand its supporting means to prevent infiltration of abrasives during the25 abrading operations.

Another object of the invention is to provide novel means for use insecuring the lenses or articles to their holding means whereby thecoeflicient of expansion of said means may be con- $0 trolled and hasparticular reference to the method of making the same. v

Other objects and advantages of the invention will become apparent fromthe following description taken in connection with the accompanying andit will be apparent that many changes may be made in the details ofconstruction, arrangement of parts and methods shown and describedwithout departing from the spirit of the invention as expressed in theaccompanying claims. We, therefore, do not wish to be limited to theexact details of construction, arrangement of parts and methods shownand described as the preferred forms only have been given by way ofillustration. Referring to the drawing:

Fig. I is a front elevation of an article to be blocked;

Fig. 11 is a sectionalview taken as on line 11-11 50 of Fig.1; and

Fig. 111 is a sectional side elevation of the device in Fig. I shown insecured relation with its holding means. i 4

. Fig. IV is a view generally similar to Fig. 55 illustrating a modifiedform of the invention. g

Lenses formed of material having roughly the characteristics ofpolymeric methyl methacrylate have all the desirable characteristics ofglass as regards transparency, index of refraction and so forth, butsuch lenses do not possess hardness 5 and resistance to attack by thecommon adhesive compounds in'general use in blocking ophthalmic lenses;Such compounds, in t e past, have been of the characteristics of'pitchor rosin which, although particularly desirable for use in blockingglass lenses, have been found to attack the polished surfaces of lensesformed of polymeric methyl methacrylate, this attack being in the natureof a solvent action which would destroy the optical, characteristics ofthe finished lens. This attack is activated bythe fact that suchadhesives are applied in a heated condition and lenses formed ,ofresinous materials of the nature described would have their surfacesmarred by the heat as .well as by the solvent action.

It, therefore, is onepf the primary objects of this invention to avoidthe above difiiculties by providing means and methods of blocking suchlenses whereby the said lenses may be quickly at- 'tached to theirholding means and danger of injury thereto obviated.

Referring more. particularly to the drawing wherein like characters ofreference designate like parts throughout the several views the deviceembodying the invention comprises a lens I, formed of polymeric methylmethacrylate or of similar artificial resins or resihoids, which isprovided with opposed optical "surfaces 2 and 3 of such curvatures thatwhen combined 'will result in the prescriptive characteristics desiredof the finished lens. The surfaces 2 and 3 are preferably formed on saidmaterial by grinding and polishing through the use of means and methodssimilar to those used in forming glass lenses. The abrading operation isperformed by the use of asuitable abrading tool having a surface thereonof a. curvature desired to be formed on one side of the lens and throughthe use of rough and successively finer abrasives used in the'art informing a. finely ground surface of the curvature of theshapeof thetool. This finely ground surface is subsequently polished by the use ofrouge or other polishing ingredients commonly used in the art infinishing such surfaces.

The lens I is secured to the block or holding means 4 by an intermediatelayer 5 of adhesive of a waxy nature. The lens is preferably firstprovided with a coating of said adhesive as by spraying, brushing ordipping-to form a thin coating 5 thereon. The face of the block orholding means 1 within desirable limits During the abrading operationsand during the finish polishing operations care is taken that the lensis properly lubricated to avoid generation of excess heat. wax becomesoftened to a state whereby the lens will move relative to the block.

The plasticity of the bees-wax may be varied by a variety of means asfollows:

constituent of the supporting material.

will dissolve or soften the v 1. There may be incorporated in thebees-wax discreet finely divided particles of the; resin itself vso thatthe wax serves as the carrier of the particles which themselves makeupthe chief In this way the coefficient of thermal expansion will besubstantially that of the resin itsel-f depending upon the amount ofresin used.

2. Fibrous materials, such as wood flour,-cotton linters or the like,may be mixed in the wax in proportions. of 10% or more of the totalamount of'wax used.

3. Blends of various waxes, such as carnauba, candelilla and so forth,may be incorporated withthe bees-wax and may in addition contain thesolid materials referred to above. The reason for the addition of thesewaxes is to produce a waxy composition having a somewhat highersoftening temperature for use during hot weather.

We have found that it may be desirable to protect the surface of theglass byapplying a layer of rubber" latex, wax emulsion, or mixtures oflatex and wax emulsions as soon as the polishing operation has beencompleted,. to protect the lens surface during the handling, incidentupon the subsequent blocking operation. This protec tive coating may beallowed to remain on the surface during blocking or may be removedtherefrom just prior to said blocking. In. the instances wherein thelayer of latex is'allowed to remain on the surface ofthe lens beingblocked the precoating of said surface with a layer of wax may beomitted if desired.

Another method of blocking consists in the formation of a sheet of waxwhich is laid upon the supporting means 4', and the lens I is" thenpressed firmly thereon so as to bring the whole assembly into bindingrelation with each other. This may be. done at room temperatures ortemperatures slightly above room temperatures but below the meltingpoint of the wax used.

The lenses may be removed from the block by emersing them into a bath ofa solvent which wax but which will have no eifect upon the resinousmaterial of the lenses. Such baths may be as follows:

If the lens is formed of a material having the characteristics ofBakelite, a bath of xvlene, toluen, benzol or the like may be used toremove the lens from the block. a

If the lens is formed of methyl methacrylate we have found thatiso-propyl alcohol is effective in removing the wax without injury tothe resin. v

- If the lens is formed of urea-formaldehyde or means 4. The materialused is bleached bees-wax and care is This is to avoid having thebeesthe like the same solvents may be used as for Bakelite.

It is to be understood that .the above solvents any desirable which willdissolve or will not injure the said solvents nature of the The block orholding are set forth only by way of illustration and that of metal,Bakelite or other desirable materials and is provided with a surface 6shaped substantially to.the shape of the adjacent finished surfaceof thelens which is to This block'is of the conventional type used in the besecured thereto.

' ophthalmic art and has an attaching stem 1 with a tapered opening 8therein adapted to fit upon the spindle of a' conventional abradingmachine.

Prior to removing the lens I from the block after the desired on saidsurface 20 surface has been formed ther' may be provided with aprotective coating of rubber latex, wax emulsion or mixtures of latexand wax emulsion as desired and 'as previously said lens has theadhesive After the block and the surmentioned above been removed'fromthe has been cleansed from face, as by'the use of any of the abovementioned solvents, the said surface may be with a protective coating'oflatex,etc., as mentioned above.

provided 30 These protective'coatings may be allowed to remain on thelens until the said lens has been edged and formed tothe contour shapedesired as is usual in the ophthalmic art. I

The lens may be ment with the shape of .the'

pressed firmly into engage- 4 by the use of a tool which thereon ofsubstantially the exposed surface of the lens and block which willsubstantially engage the entire area of said lens.

lens during th It is to be able means an This will avoid distorting ofthe e blocking operation.

understood that any other'desird methods may be used'in pressing thelens into engagement with the adhesive means on the The blanks givestandard instance, the

chanical means such plurality of spaced projections throughout thecontour of th against latera ing and polishing operations.

block.

may, if desired, be preformed to contour shapes and sizes, in whichblock may be provided with meas an integral lip9 or a e block forholding the said lens l displacement during the abrad- The height of thelip above the'face 6 of the block will be such as to allow the tool usedin abrading the exposed surface of the face and permit the said toolsired amount lens free movement over said sur- I to remove the defromsaid surface to reduce the lens toa given minimum thickness.

As previously stated performing th above the tools used in m e abradingor polishing operationsand the machines utilized in performing saidoperations ma in abrading lenses in From the foregoing description itwill be seen that simple, efiicient and tmethods have y be of theconventional typeused the ophthalmic art.

economical means and been provided for blocking resinous articles suchas lenses for the performing of abrading danger of inluryto the finishedsurfaces-on said operations thereon wherein (the lenses is obviated.

Having desc ribed our invention, we claim:

1. A device for use in supporting lenses, during the abrading thereof,the characteristics of methyl 5 terial having which are formed of mathanthat of the methacrylate comprising a holder having a lens supportingsurface of substantially thesame radius of curvature as a finishedsurface of the lens to be supported, and adhesive means, of acomposition containing bees-wax and discreet finely divided particles ofresinous material which make up the chief constituent of said adhesive,on said lens supporting surface and in holding relation therewith andwith the finished surface of the lens to be supported, said compositionhaving a softening temperature which is lower methyl methacrylate andadhesive characteristics which will not destroy or alter the surfacequality or other optical characteristics possessed by said lens surfacewith which it engages, during the holding and abrading of said lens.

2. A device for use in supporting lenses formed of material havingcharacteristics similar to of comprising a holder having methylmethacrylate during the abrading therea lens supporting surface, andadhesive means, of a waxy composition, on said lens supporting surfaceand in holding relation therewith and with a finished to be supported,said waxy composition comprising a mixture of wax and fibrous materialsin proportions of 10% or more of the total amount of wax used, said waxycomposition having a softening temperature which is lower than that ofmethyl methacrylate and having adhesive characteristics which will notalter the surface quality or other optical characteristics possessed bythe finished optical surface of said lens prior to being supported bysaid supporting surface, during the holding and abrading of said lens.

, EDGAR D. Till-YER.

HAROLD R. MOULTON.

